Lock up clutch control

ABSTRACT

A control for a transmission having a fluid coupling and a lock up clutch for selectively providing a fluid or mechanical input from a gas turbine engine. A shift valve controls the engagement and disengagement of the lock up clutch in response to a transmission output governor signal or a manual signal in cooperation with the governor signal. The manual signal is controlled by a control valve which also supplies a disengagement bias pressure to the shift valve when the manual signal is not directed to the shift valve. The manual signal is generated in response to an engine operating parameter, such as torque demand, and acts on the shift valve in such a manner as to prevent engagement of the lock up clutch at zero vehicle speed above a predetermined value of the operating parameter.

United States Patent [1 1 1 March 6, 1973 Edmonds LOCK UP CLUTCH CONTROL[7 51 Inventor: I John 0. Edmunds, Indianapolis, Ind.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[221 Filed: Aug. 5, 1971 [211 Appl. No.: 169,377

[52] US. Cl. ..74/645, 74/733, 192/329 [51] Int. Cl. ..F16h 47/08, B60k21/02 [58] Field of Search ..74/645 [56] References Cited UNITED STATESPATENTS 2,726,557 12/1955 Ackerman ..74/645 X 2,734,399 2/1956Christenson ..74/645 X 3,073,179 l/1963 Christenson ..74/645 PrimaryExaminerCharles .1. Myhre Assistant Examiner-Thomas C. Perry Attorney-W.E. Finken et al.

[57] ABSTRACT A control for a transmission having a fluid coupling and alock up clutch for selectively providing a fluid or mechanical inputfrom a gas turbine engine. A shift valve controls the engagement anddisengagement of the lock up clutch in response to a transmission outputgovernor signal or a manual signal in cooperation with the governorsignal. The manual signal is controlled by a control valve which alsosupplies a disengagement bias pressure to the shift valve when themanual signal is not directed to the shift valve. The manual signal isgenerated in response to an engine operating parameter, such as torquedemand, and acts on the shift valve in such amanner as to preventengagement of the lock up clutchat zero vehicle speed above apredetermined value of the operating parameter.

3 Claims, 2 Drawing Figures TURBINE GAS ENGINE i/[VII LOCK-UP SHIFTVALVE 452 gsl a J g 16 6 a; DR3 DR4 .CONTROL w EX VALVE g1 LOCK UPCLUTCH CONTROL This invention is related to lock up clutch controls andmore particularly to controls providing automatic and selectiveengagement of the lock up clutch.

When combining a multi-range transmission and a gas turbine engine it isoften desirable to use a fluid coupling between the engine andtransmission so that the engine may run freely at idle conditions.However, in many instances it is desirable to directly couple the engineand transmission to provide maximum tractive effort for maximumacceleration of the vehicle from the idle condition. Therefore, a lockup clutch is incorporated in the transmission to provide a mechanicaldrive connection between the engine and the transmission gearing. Topermit selective engagement and disengagement of the lock up clutch acontrol must be provided. The present invention provides such a controlthrough the selective operation of a shift valve and a control valve.The shift valve controls the engagement and disengagement of the lock upclutch and is biased toward the disengaged position by a bias spring anda bias pressure supplied by the control valve. During normal operationthe shift valve is upshifted by transmission governor pressure acting inopposition to the bias pressure. However, if the operator desires tohave maximum starting tractive effort, the control valve may be shiftedby manual valve to permit an engagement bias pressure to be directed tothe lock up shift valve while exhausting the disengaging bias pressure.The engagement bias pressure is preferably inversely proportional toengine torque demand or engine power output so that the shift valvecannot be shifted above a predetermined engine torque output at zerovehicle speeds. The control is tailored so that the lock up clutch canbe engaged at higher throttle settings with increased vehicle speeds.

It is, therefore, an object of this invention to provide in an improvedcontrol for an engine driven multirange transmission having a lock upclutch, a shift valve responsive to governor pressure to provide anautomatic engagement of the lock up clutch and a control valveresponsive to a manual valve for selectively controlling the shiftvalve.

It is another object of this invention to provide in an improved controlfor controlling a lock up clutch a shift valve for controlling theengagement and disengagement of the lock up clutch and a control valveoperable in one position to provide a disengagement bias pressure to theshift valve and selectively movable to another position to provide anengagement bias pressure to the shift valve to permit selectiveengagement of the lock up clutch.

Another object of this invention is to provide in an improvedtransmission control a shift valve responsive to governor pressure forproviding automatic engagement of a lock up clutch and a control valvecooperating with the shift valve for permitting selective engagement ofthe lock up clutch when the transmission is operated according to apredetermined engine throttle and vehicle speed characteristic.

Another object of this invention is to provide an improved controlhaving a shift valve and control valve for providing automaticengagement of a clutch in one throttle setting range at a fixedtransmission speed and in another throttle range at various transmissionspeed and providing manual selective engagement of the clutch below apredetermined throttle setting at zero vehicle speed and at or belowincreased throttle settings with increased vehicle speed.

These and other objects and advantages of the present invention will bemore apparent from the following description and drawings in which:

FIG. 1 is a diagrammatic view of the control; and

FIG. 2 is a curve depicting selective and automatic operation of thecontrol.

Referring to FIG. 1 wherein like characters represent the same orcorresponding parts there is shown a conventional gear pump 10 whichdraws fluid from a reservoir 12 through a passage 14 and delivers fluidthrough a main passage 16 to a manual selector valve 18 and modulatorvalve 20, a lock up shift valve 22 and a transmission output governor24. Pressure in main passage 16 is controlled by a regulator valve 25.The governor 24 is a conventional fluid governor which supplies a fluidpressure in proportion to speed and is connected to be driven by theoutput shaft of the transmission 26. The transmission is driven by a gasturbine engine 28 through a fluid coupling 30 and provides selectivedrive ranges including a low range. The transmission 26 may be connecteddirectly to the engine 28 by a lock up clutch 32. A more completedescription of the transmission 26 may be found in U.S. Ser. No.104,867, filed Jan. 8, 1971 and assigned to the assignee of thisinvention.

The manual selector valve 18 includes a valve spool 34 having threeequal diameter spaced lands a, b, and c slidably disposed in a valvebore 36 which is in fluid communication with the main passage 16. Alsoin fluid communication with the valve bore 36 is a reverse passage 38, adrive four (DR 4) passage 39, a hold passage 40, a drive three (DR 3)passage 42, a drive two (DR 2) passage 44 and a drive one (DR 1) passage46 and a pair of exhaust passages 48. The valve spool 34 is selectivelymovable in the valve bore 36 to permit fluid communication between themain passage 16 and the various drive passages 38, 39, 42, 44 and 46.The passage 42 is in fluid communication with the passage 40 through ahold regulator valve 50 which is described in detail in U. S. Ser. No.104,867, which also describes the fluid connections from the selectorvalve 18 to a plurality of shift valves and relay valves which provideselective and automatic shift control for the drive ranges of thetransmission 26. The drive one passage 46 is in fluid communication withthe chamber 52 which is part of a control valve generally designated 54.

The modulator valve 20 is in fluid communication via a passage 56 withthe gas turbine engine 28 and receives therefrom a pressure signalproportionalto compressor discharge pressure. The modulator valve 20provides a modulator pressure inversely proportional to engine torquedemand or power developed and has a valve element 58 having equaldiameter spaced lands a and b slidably disposed in a valve bore 60. Abias spring 62 located in a spring chamber 64 vented by an exhaustpassage 66 biases the valve element 58 to an open position connectingmain passage 16 with a modulator pressure passage 68 between lands a andb. The modulator pressure passage 68 is connected through a restriction70 to a chamber 72 at one end of valve bore 60 adjacent the end of landb. Pressure in chamber 72 biases the valve element 58 against the spring62 to connect the modulator pressure passage 68 to an exhaust passage74. A bias force directly proportional to compressor discharge pressureis also imposed on the valve element 58 through an actuator stem 76slidably mounted in a bore 78. One end of the bore 78 is exhaustedthrough passage 80 while the other end of the bore is in communicationwith a chamber 82 which is connected to the compressor of the gasturbine engine. The actuator stem 76 engages a pin 84 which is slidablydisposed in a valve bore 86 and abuts valve land b of valve element 58.The force imposed on the actuator stem 76 and therefore the pin 84 isdirectly proportional to the compressor discharge pressure and thereforeincreases with increasing compressor discharge pressure. This force actsin opposition to the bias spring 62 thereby decreasing the bias on thevalve element 58 as compressor discharge pressure increases so that aregulated pressure in modulator pressure passage 68 develops which isinversely proportional to compressor discharge pressure.

The lock up shift valve 22 includes a valve element 88 having steppeddiameters a, b and c which are slidably disposed in stepped diameterbores 90, 92, 94 respectively. The valve element 88 has a reduced stemportion 96 located between lands a and b to permit selective fluidcommunication between mainline passage 16 and a lock up clutchengagement passage 98 which is in fluid communication with the lock upclutch 32 and between the passage 98 and an exhaust passage 102. Thefree end of land a is in fluid communication with a governor passage 100which supplies the governor pressure thereto from the transmissionoutput governor 24. In the position shown, which is in the lock upclutch disengagement position, lock up pressure passage 98 is exhaustedto permit disengagement of the lock up clutch 32. The valve element 88is biased to the disengaged position shown by a bias spring 104 which islocated in a bias chamber 106 which is in fluid communication with adisengagement bias pressure passage 108 connected to the control valve54. The differential area between lands b and c is in fluidcommunication with an engagement bias pressure passage 110 which is alsoconnected with the control valve 54. The valve element 88 has twodifferential areas, namely, between lands a and b and lands b and cwhich provide piston areas for linear fluid motors. The ends of valveelement 88 are in closed chambers so that they may act as pistons forlinear fluid motors. It is obvious from the above description that fourseparate linear fluid motors are provided.

The control valve 54 has a valve element 112 having equal diameterspaced lands a and b slidably disposed in a valve bore 114 and a largerdiameter land c slidably disposed in a valve bore 116. The valve bore114 is in fluid communication with the chamber 52 and exhausts passage118, the engagement bias pressure passage 110 and the modulator pressurepassage 68. The disengagement bias pressure passage 108 is in fluidcommunication with both bores 114 and 116 while valve bore 116 is influid communication with an exhaust passage 120. The valve spool l 12 isbiased to the left by a spring 122. When the valve spool 112 is movedfully to the left, modulator pressure in passage 68 is directed betweenlands b and 0 through passage 108 to the chamber 106. This modulatorpressure also acts on the differential area between lands b and c tomove the valve spool l 12 to the right against spring 122 therebylimiting the maximum value of the pressure available in chamber 106. Asmentioned previously, the pressure in passage 68 decreases as compressordischarge pressure increases therefore as engine torque demand or powerdeveloped increases the pressure in passage 68 decreases until thepressure acting on the differential area of lands b and 0 cannotovercome the force in spring 122 at which time the disengagement biaspressure in chamber 106 will be equal to the modulator pressure inpassage 68. When the selector valve 18 is moved to the drive one or lowrange position the chamber 52 is pressurized which will cause the valvespool 112 to move fully to the right against the spring 122 until thefree end of valve land 0 comes into contact with a stop member 124. Atthis time the modulator pressure passage 68 will be in fluidcommunication with the engagement bias pressure passage between lands aand b of valve element 1 12. Also, at this time the disengagement biaspressure passage 108 will be exhausted between lands b and 0 throughpassage 120. If the modulator pressure in passage 68 and passage 110 issufflciently high so that the force applied to the differential areabetween lands b and c of valve element 88 can overcome the force inspring 104, the lock up shift valve 22 will move to the engagementposition thereby connecting mainline passage 16 with the lock up clutchpressure passage 98 to engage the lock up clutch 32. At low throttlesettings the modulator pressure will be sufficiently high to cause thelock up shift valve 22 to assume the engaged position. This is shown bythe point on curve 132 of FIG. 2. If the engine throttle setting ishigher than point 130, the modulator pressure will not be sufficientlyhigh at zero vehicle speed to cause the lock up shift valve 22 to move.Thus, at this time the connection between the gas turbine engine 28 andthe transmission 26- will be through the fluid coupling 30. However, asthe vehicle speed increases, governor pressure acting on the free end ofvalve land a of valve element 88 will increase and will be added tothe'force of a modulator pressure on the differential area between landsb and c so that at some higher vehicle speed, along curve 132, the lockup clutch 32 will be engaged. At point 134 on curve 132 the combinationof modulator pressure and governor pressure will be sufficient tooperate the lock up shift valve even though the modulator pressurecorresponds to the full throttle setting of the engine 28. Ifthethrottle setting is below the point 130 on curve 132, the lock upclutch will be engaged at zero vehicle speed. Once the lock up shiftvalve 22 is moved to the engaged position and the lock up clutch 32 isengaged, main pressure acting on the differential area between lands aand b of valve element 88 assists the modulator pressure bias in passage110 and the governor pressure bias in passage 100 to hold the valveelement 88 in the shifted position so that the lock up valve 22 willremain shifted even though the modulator chamber 106 acting on valveland c. For throttle settings between points 134 and 138 on curve 136 itis seen that the disengaging bias pressure is variable so that asvehicle speed increases beyond point 134 the lock up clutch 32 will beautomatically engaged at lesser throttle setting. At throttle settingscorresponding to point 138 the disengaging bias pressure in passage 108becomes constant so that a constant bias force, as established by thedifferential area between lands b and c of valve element 112 and thespring 122, is applied to the valve element 112. Therefore, at vehiclespeeds higher than point 138 the lock up clutch 32 will be engagedautomatically and independently of the throttle position. As mentionedabove, after the lock up valve 22 has shifted line pressure in passage16 provides a hysteresis force on the valve element 88 so thatdisengagement of the lock up clutch occurs at lower vehicle speeds for acorresponding throttle setting. This is shown by curve 140 in FIG. 2. Asshown by curve 140, the lock up clutch will stay engaged until thevehicle speed is equal to or less than the point 142 provided thethrottle setting is below the point represented by point 142. Tomaintain the lock up clutch engaged at low vehicle speeds correspondinghigher throttle settings are required so that the lock up clutch willremain engaged down to zero vehicle speed at a throttle settingestablished at point 144.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A control for an engine driven multi-range transmission having afluid coupling, and a fluid operated selectively operable lock upclutch, said control comprising, a source of fluid pressure; selectorvalve means in fluid communication with said source for selecting aplurality of drive ranges including a low range, modulator valve meansin fluid communication with said source and operatively connected withthe engine for generating a modulated fluid pressure in response to anoperating parameter of the engine; governor means for providing agovernor pressure proportional to the output speed of the transmission;shift valve means in fluid communication with said source, said governormeans, and said lock up clutch and being movable to engaged anddisengaged positions for controlling the operation of said lock upclutch; and control valve means in fluid communication with saidmodulator valve means, said selector valve means and said shift valvemeans and being operable to supply a disengaging bias pressure to saidshift valve means when said selector valve is in a position other thansaid low range, and operable to supply modulated'fluid pressure to saidshift valve to provide an engaging bias pressure to said shift valvewhen said selector valve is in said low range.

2. A control for an engine driven multi-range transmission having afluid coupling, and a fluid operated selectively operable lock upclutch; said control comprising, a source of fluid pressure; selectorvalve means in fluid communication with said source for selecting aplurality of drive ranges including a low range, modulator valve meansin fluid communication with said source and operatively connected withthe engine for generating a variable modulated fluid pressure inresponse to an operating parameter of the engine; governor means forproviding a governor pressure proportional to the output speed of thetransmission; shift valve means in fluid communication with said source,said governor means, and said lock up clutch and being movable toengaged and disengaged positions for controlling the operation of saidlock up clutch; and control valve means in fluid communication with saidmodulator valve means, said selector valve means and said shift valvemeans and being operable to supply a fixed disengaging bias pressure tosaid shift valve means when said selector valve is in a position otherthan said low range and when said modulator pressure is above apredetermined value and a bias pressure equal to said modulator pressurebelow the predetermined value, and operable to supply modulated fluidpressure to said shift valve to provide an engaging bias pressure tosaid shift valve'while exhausting the disengaging bias pressure whensaid selector valve is in said low range.

3. A control for an engine driven multi-range transmission having afluid coupling, and a fluid operated selectively operable lock upclutch; a source of fluid pressure; selector valve means in fluidcommunication with said source for selecting a plurality of drive rangesincluding a low range, modulator valve means in fluid communication withsaid source and operatively connected with the engine for generating avariable modulated fluid pressure in response to an operating parameterof the engine; governor means for providing a governor pressureproportional to the output speed of the transmission, shift valve meansin fluid communication with said source, said governor means, and saidlock up clutch and being movable to engaged and disengaged positions forcontrolling the operation of said lock up clutch; and control valvemeans in fluid communication with said modulator valve means, saidselector valve means and said shift valve means and being operable tosupply a fixed disengaging bias pressure to said shift valve means whensaid selector valve is in a position other than said low range, andoperable to supply modulated fluid pressure to said shift valve to movesaid shift valve to the engaged position when said modulator pressure isabove a predetermined value and when said selector valve is in said lowrange.

1. A control for an engine driven multi-range transmission having afluid coupling, and a fluid operated selectively operable lock upclutch, said control comprising, a source of fluid pressure; selectorvalve means in fluid communication with said source for selecting aplurality of drive ranges including a low range, modulator valve meansin fluid communication with said source and operatively connected withthe engine for generating a modulated fluid pressure in response to anoperating parameter of the engine; governor means for providing agovernor pressure proportional to the output speed of the transmission;shift valve means in fluid communication with said source, said governormeans, and said lock up clutch and being movable to engaged anddisengaged positions for controlling the operation of said lock upclutch; and control valve means in fluid communication with saidmodulator valve means, said selector valve means and said shift valvemeans and being operable to supply a disengaging bias pressure to saidshift valve means when said selector valve is in a position other thansaid low range, and operable to supply modulated fluid pressure to saidshift valve to provide an engaging bias pressure to said shift valvewhen said selector valve is in said low range.
 1. A control for anengine driven multi-range transmission having a fluid coupling, and afluid operated selectively operable lock up clutch, said controlcomprising, a source of fluid pressure; selector valve means in fluidcommunication with said source for selecting a plurality of drive rangesincluding a low range, modulator valve means in fluid communication withsaid source and operatively connected with the engine for generating amodulated fluid pressure in response to an operating parameter of theengine; governor means for providing a governor pressure proportional tothe output speed of the transmission; shift valve means in fluidcommunication with said source, said governor means, and said lock upclutch and being movable to engaged and disengaged positions forcontrolling the operation of said lock up clutch; and control valvemeans in fluid communication with said modulator valve means, saidselector valve means and said shift valve means and being operable tosupply a disengaging bias pressure to said shift valve means when saidselector valve is in a position other than said low range, and operableto supply modulated fluid pressure to said shift valve to provide anengaging bias pressure to said shift valve when said selector valve isin said low range.
 2. A control for an engine driven multi-rangetransmission having a fluid coupling, and a fluid operated selectivelyoperable lock up clutch; said control comprising, a source of fluidpressure; selector valve means in fluid communication with said sourcefor selecting a plurality of drive ranges including a low range,modulator valve means in fluid communication with said source andoperatively connected with the engine for generating a variablemodulated fluid pressure in response to an operating parameter of theengine; governor means for providing a governor pressure proportional tothe output speed of the transmission; shift valve means in fluidcommunication with said source, said governor means, and said lock upclutch and being movable to engaged and disengaged positions forcontrolling the operation of said lock up clutch; and control valvemeans in fluid communication with said modulator valve means, saidselector valve means and said shift valve means and being operable tosupply a fixed disengaging bias pressure to said shift valve means whensaid selector valve is in a position other than said low range and whensaid modulator pressure is above a predetermined value and a biaspressure equal to said modulator pressure below the predetermined value,and operable to supply modulated fluid pressure to said shift valve toprovide an engaging bias pressure to said shift valve while exhaustingthe disengaging bias pressure when said selector valve is in said lowrange.